Demonstration of Interference (to Show Sound is a Wave Motion), Using Speakers
Apparatus Two speakers, signal generator
Procedure Connect both speakers to the same signal generator and set to same frequency. Walk in a straight line in front of speakers, as illustrated in Fig 11.2.
Observation There will be an increase and decrease in the intensity of sound due to interference of the waves produced by each speaker.
Loudspeakers Signal generator Fig 11.2
Conclusion As only waves undergo the phenomena of interference it can be concluded that sound is a wave motion.
B A
DEMONSTRATION 11.2
Demonstration of Interference (to Show Sound is a Wave Motion), Using a Tuning Fork
Apparatus Tuning fork
Procedure Strike the tuning fork. Bring the fork close to your ear and rotate.
Observation There will be an increase and decrease in the intensity of sound due to interference of the waves produced at each prong of the fork.
Conclusion As only waves undergo the phenomena of interference, it can be concluded that sound is a wave motion.
Fig 11.3
SCIENCE,TECHNOLOGY & SOCIETY
Reduction of noise using destructive interference In industry, many machines produce a constant noise. A sensor can be used to pick up the frequency of this sound and the same sound wave can be produced. If the artificial noise is out of phase with the machine noise, destructive inter- ference occurs and the intensity of the noise pollution is reduced. It’s the one occasion where two wrongs do make a right!
